Polyurethane elastomers are widely used in such diverse applications as gasketing and sealing materials, medical devices, ski boots, jounce bumpers, and conveyor rollers, to name but a few. Due to their strength, hardness, and other properties, elastomers prepared from isocyanate-terminated prepolymers incorporating polytetramethylene ether glycol (PTMEG) and polyester polyols are dominant in demanding applications. The PTMEG and polyester polyol components are termed "crystallizable" polyols, due to their stress-induced molecular alignment into configurations which resemble crystalline structures. Polyoxyethylene glycols are further examples of crystallizable polyols. The "crystalline" alignment, together with the intermolecular forces such as polar attractions and van der Waals attractions which such alignments induce, are believed responsible for the desirable physical properties demonstrated by such elastomers. See, e.g., "Comparison of the Dynamic Properties of Polyurethane Elastomers Based on Low Unsaturation Polyoxypropylene Glycols and Poly(tetramethylene oxide) Glycols," A. T. Chen et al., Polyurethane World Congress 1993, pp. 388-399.
PTMEG, polyester polyols and "crystallizable" polyols other than polyoxyethylene glycols tend to be high cost starting materials, however. As a result, polyurethane elastomers prepared from these components also are higher priced products. Moreover, the elongations of elastomers prepared from crystallizable polyols are generally limited to the range of 400 to 600 percent. Elongations can be increased by adding materials such as plasticizers or mono-functional reactive species to serve as chain terminators. However, any increase in elongation is obtained only at the expense of marked reduction in tensile strength, usually accompanied also by a decrease in hardness. It would be desirable to increase both elongation and tensile strength in elastomers prepared from crystallizable polyols.
Polyoxypropylene diols having low unsaturation have been suggested to wholly replace PTMEG in elastomer prepolymer formulations, however, the properties of the resulting elastomers are little improved, exhibiting somewhat improved tear strength but similar tensile strengths and elongations. See, A. T. Chen, op.cit. However, in many applicaitons, it would be desirable to retain the known benefits of crystallizable polyol-based elastomers while being able to improve properties such as tensile strength and elongation.